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8/9/2019 LPI 101 Ch09 Startup and Shutdown
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SAIGONLAB 83 Nguyn Th Nh, P9, Q.Tn Bnh, Tp. HCM LPI 102
Chapter 9
System Startup and Shutdown
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SAIGONLAB 83 Nguyn Th Nh, P9, Q.Tn Bnh, Tp. HCM LPI 102
Objectives
Define and explain bootstrap procedure
Explain single and multi-user run levels
Identify and configure system startup files
Perform a clean shutdown procedure
Explain and define the maintainance mode
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Standard Boot Process (LILO)
System load the Linux bootstrap from default boot device,
LILO (GRUB), which resides in Master Boot Record of
hard drive
The
bootstrap program has abi
li
ty to boot Li
nux
to si
ngle-
user or multi-user mode
After the bootstrap has loaded the kernel ( stored in the
/boot or / partition ) into memory, it relinquishes control to
this system
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Standard Boot Process (LILO)
The Linux system initializes physical devices, virtual
memory controller, and its internal control tables for
processes, files, ..
The
i
ni
t proce
ssi
s starte
d andi
t starts all othe
r use
rprocesses
Before handing control over init, the kernel will create any
other kernel threads
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Boot Problems
Sometimes, lilo will not able to boot the system, it prints the
letters LILO on screen. The problems: diskcorrupted, the
information on diskgeometry is incorrect, or since the new
kernel imageis installed
Troubleshooting: boot the system from bootable CD or
floppy and try to repair disk problems or correct the
/etc/lilo.conf
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Manual Boot
There are times when lilo has loaded the kernel but the kernel
does NOT work properly because some of hardware can not
befound,Its possible topass configuration to the kernel
through lilo at lilo command line when booting:
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Manual Boot
List of someimportant boot prompt arguments :
root=/dev/hda1 Tell the kernel which device to be mounted asroot file system
ramdisk_size=2MB Define maximum of ramdisk (up to 4MB )single This actually is a parameter passed to init,
causes the system to boot in single-usermode
mem=192MB Tell the kernel amount ofmemory ( RAM size )
aha1542=0x334 Set the I/O port address for SCSI Interface Card
hdc=cdrom Specifies the third disk deviceis a CD-ROM
Instead of typing them at each reboot, these arguments can beincluded into the lilo.conf :
append=hdc=cdrom
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Manual Boot
Moreinformation about boot prompt and arguments can be
found at:
http://www.tldp.org/HOWTO/BootPrompt-HOWTO.html
Refers to man 5 lilo.conffor a detailed information aboutarguments
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Startup Flow Control
It used to run Linux system at level 3
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Run Levels
Runlevel 0/etc/rc.d/rc0.d
Shutdown mode. Tasks: killing all processesand unmounting file systems
Runlevel 1/etc/rc.d/rc1.d
Single-user mode, generally used by systemadministrator when doingmaintenance/recovery of the system
Runlevel 2/etc/rc.d/rc2.d
Multi-user mode, some network services arenot started : NFS,
Runlevel 3/etc/rc.d/rc3.d
Multi-user mode, all network services arestarted
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Run Levels
Runlevel 4/etc/rc.d/rc4.d
User defined run level
Runlevel 5/etc/rc.d/rc5.d
Multi-user X11 mode. All services that arestarted in run level 3 are generally started
Runlevel 6/etc/rc.d/rc6.d
Reboot runlevel.
Runlevel s/S/etc/rc.d/rcS.d
Single-user mode.
Runlevel a/b/c Pseudo states. (rarely used)
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Run Levels Using
Use /sbin/runlevel to get current run level
How to start X window ?
RedHat and TurboLinux : # init 5
Debian : # init 2 SuSE and Caldera: # init 3
Slackware : # init 4
Re
boot : #i
ni
t 6 Shutdown : # init 0
To manual set default run level at boot time, open
/etc/inittab and lookfor this line : id:5:initdefault:
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Structure of/etc/inittab
Each line has 4 fields seperated by colons:
id:level:action:command
id Uniqueidentifier for line (up to 4 alphanumericcharacters)
level Run level(s) to activate processs
action Keyword for how to run processcommand Full path name and parameters of command to
beexecuted
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Structure of/etc/inittab
The main inittab action keywords are:
Off Do not run this command. Used to retain an entry butto disableit.
wait Run command and wait for completion
once Run command but do not wait. Daemons processesare often started this way
respawn Run command; If process exists, then rerun it. Usedfor commands that have to start again aftercompletion, like getty and ttymon
sysinit Run command at first init
boot Run command at boot time but do not wait
bootwait Like boot but wait for completion
initdefault Defines default boot level
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/etc/inittab
# more /etc/inittab
id:3:initdefault:
#System initialization
si::sysinit:/etc/rc.d/rc.sysinit
l0:0:wait:/etc/rc.d/rc 0
l1:1:wait:/etc/rc.d/rc 1
l2:2:wait:/etc/rc.d/rc 2
l3:3:wait:/etc/rc.d/rc 3
l4:4:wait:/etc/rc.d/rc 4
l5:5:wait:/etc/rc.d/rc 5
l6:6:wait:/etc/rc.d/rc 6
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Run Command Scripts
The run commands scripts are kept under /etc/rc.d/ and areinitiated by init with directions from /etc/inittab
The script called rc itself runs startup programs in sub-
di
re
ctorie
s unde
r /e
tc/rc.d/ rc 0 looks in /etc/rc.d/rc0.d for runlevel 0
rc 1 looks in /etc/rc.d/rc1.d for runlevel 1
rc 2 looks in /etc/rc.d/rc2.d for runlevel 2
etc
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Run Command Scripts
These startup programs are symbolic links to the actualscripts in the /etc/init.d/
The startup link names areformatted:firstcharacter isS
(starte
d) orK(ki
lle
d or stoppe
d), the
next two digitsi
de
ntif
ytheorderthat scripts areexecuted by rc program
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Changing Run Levels
Useinit command to change between run levels. Syntax :
init
Examples :
# init 0 Shutdown system
# init 6 Reboot system
# init 3 Change to runlevel 3, multi-user text mode
# init 5 Change to runlevel 5, multi-user X11 mode
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Shuting Down
Use shutdown commansd. It differs from init 0 whenallowing to specify time to exit, warn users what happens,
Make sure that you follow the proper shutdown procedure.
Do NOT simply shut off the power
# shutdown Default system shutdown (run level1)
# shutdown r now R eboot the system now (run level6)
# shutdown h 2:00 Halt the system at 2:00AM (runlevel 0)
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Maintenance Mode
When the system doesnt work because problems. Thesimplest and best solution is to shut down the system to
maintenance mode (run level 1) or reboot the system to
single-user mode (run level S) and try to fix problems
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